1) Buy domain and attach google apps to it.
2) Switch catch-all email setting in preferences.
3) When register for a service use email like email@example.com or firstname.lastname@example.org etc.
So if your goal is to maintain email-provider independence, then relying on provider-specific features like the '+' modifier works against that goal.
For me though, the main reason I don't use it is most sites that I want to use it on reject the '+' in the address as invalid. It happens enough that I don't bother trying anymore.